A long term evolution (LTE) network is a long term evolution project of the 3rd generation partnership project (3GPP). As a kind of communication standard to be used widely, it is required to have a higher transmission rate and a better transmission quality. To meet these requirements, accurate downlink channel estimation is an indispensable part.
In an example of the prior art, a downlink channel estimation method in an LTE network is described, and the method is summarized as follows: a base station (Node B), by using a resource element (RE) of a resource block (RB) allocated to a mobile terminal, transmits a reference signal (RS) to the mobile terminal; after receiving the signal on the RE, the mobile terminal can estimate the channel response on the RE with a common RS; after estimating the channel response on the RE, the mobile terminal can further obtain the channel responses on other REs of the RB in an interpolation method, thereby completing downlink channel estimation. Where, an RE is the smallest unit of an RB, and one RE usually contains an orthogonal frequency division multiplexing (OFDM) symbol and a sub-carrier. Specifically, in the method described in the above example of the prior art, RSs transmitted by the base station are dispersed sparsely on the RBs of the mobile terminal, and a distribution diagram of RSs is shown in FIG. 1 in which a scene that RSs are distributed on two adjacent RBs is illustrated. Where, RSs are dispersed on four REs of each RB; a grid refers to a RE, and/refers to a RB index. It is assumed that a signal received by the mobile terminal on a RE in FIG. 1 is y=hs+n; where h refers to the channel response on the RE, s refers to a RS, and n refers to an additive noise. If the statistical properties of h and n are unknown, the mobile terminal can estimate h through zero-forcing: ĥ=y/s; and if the statistical properties of h and n are known, the mobile terminal can estimate h by using a minimum mean square error (MMSE). Here, It is assumed that the mean value of h is zero, the variance of n is νh2, and the variance of n is N0, therefore, the estimated value is
            h      ^        =                                        σ            h            2                    ⁢                                                  s                                      2                                                              σ              h              2                        ⁢                                                          s                                            2                                +                      N            0                              ⁢      y        ;where ∥s∥ refers to an absolute value of RS. After estimating a RE channel response, the mobile terminal can obtain the channel responses on other REs by an interpolation method. In the method described in the prior art 1, errors of channel estimation mainly come from two aspects: one is an estimation error ∥h−ĥ∥ of the channel responses on the RE; the other is an error caused by interpolating.
In another example of the prior art, another downlink channel estimation method in an LTE network based on the above example of the prior art is described, and the method is summarized as follows: firstly, a mobile terminal preliminarily estimates a RE channel response allocated to the mobile terminal according to the method described in the above example of the prior art; then, the mobile terminal demodulates a data signal by using the preliminarily estimated channel response, where the demodulated data signal can be a data signal on an RE with a smaller detection error probability; and finally, the mobile terminal can take the demodulated data signal as a new RS to re-estimate the RE channel response, therefore, the accuracy of channel estimation can be improved. But in an actual application, if the mobile terminal is located in the central area of a cell, a transmission power of data signals transmitted from a base station to the mobile terminal is relatively small (generally 3 dB smaller than that of common RSs), and if the mobile terminal still takes the demodulated data signal as an RS to re-estimate the RE channel response, a larger error would be introduced, thereby reducing the accuracy of downlink channel estimation.
Therefore, when the mobile terminal is located in the central area of a cell, how to improve the accuracy of downlink channel estimation is an urgent problem to be solved in this field.